"I don't think anyone is too big to indict, no one is too big to jail," Bharara said. "There's enough moral hazard in the industry. If you give people a blank check and tell them they have a get-out-of-jail-free card because of their size...that's a very dangerous thing."

The office has been involved recently in some high-profile cases, particularly the insider-trading probe involving hedge fund SAC Capital, which is run by Stephen A. Cohen.

While he wouldn't address any cases specifically, Bharara said the best thing anyone can do when they cross paths with his office is cooperate.

"It's not a laughing matter and it's not a joking matter," he said. "You should take it very seriously. The smartest thing you could think about doing at the moment is think about how forthcoming you're going to be and how cooperative you should be."

On his way over to the conference, at the Pierre Hotel in Manhattan, he said he had some subpoenas with him but ran into "like six corrupt politicians" on the way.

More seriously, though, he cautioned against "armchair quarterbacks" and those in the press who try to read tea leaves and discern the office's intentions.

And he pledged that the office would not simply seek fines for continued bad behavior.

"If you're an institution that has on multiple occasions committed misconduct and the first time you get fined and the second time you get fined and the third time you get a fine, at some point you have to be held responsible in a more serious way," he said. "Otherwise, you don't get the message."